The correct answer is D. All of the above.
National expenditure is the total amount of money spent by all the people and businesses in a country in a given period of time. It is usually measured in terms of gross domestic product (GDP), which is the total market value of all the goods and services produced in a country in a given year.
Consumption expenditure is the total amount of money spent by households on goods and services. It includes spending on food, clothing, housing, transportation, entertainment, and other goods and services.
Investment expenditure is the total amount of money spent by businesses on new capital goods, such as factories, machinery, and equipment. It also includes spending on research and development, and on new products and services.
Government expenditure is the total amount of money spent by the government on goods and services, such as education, healthcare, and defense. It also includes transfer payments, such as Social Security and unemployment benefits.
National expenditure is important because it is a measure of the economic activity in a country. It is also used to calculate other economic indicators, such as the gross national product (GNP) and the unemployment rate.